What is a Variable?

Global Variables store information referenced and manipulated by the model. Variables are global, meaning they can be seen and changed by the action of any entity from anywhere in the model. Variables can be set, incremented, decremented, and examined in the Action tab of the dialog — Access and use variables in many fields in dialogs throughout ProcessModel.

Values written to a variable are summarized in the output tables, may be plotted to a time-series graph, summarized in a histogram, and exported to Excel.

Examples of variable usage

Variables record changes during the simulation

To see the volume of people in a waiting room over time, INC (increment) a variable when people arrive and DEC (decrement) when people leave.

INC increases the value of the variable by one.
DEC decrements the value of the variable when a person leaves by one.

A plot of the variable shows the value over time. Charts such as the one below are easily accessible and valuable for uncovering opportunities. See How do I use Smart Stats?

Variable changes plotted over time offer insight into problems and solutions.

A variable changed in one area of the model allows a gate to open and close in another model area.

Several Model Objects provide the functionality of a gate. Each of the gate model objects (1-11) uses a variable to signal when the gate opens and closes. The variable combines with a trigger activity and a Wait Until statement. See What is a Trigger Activity? What is a Wait Until statement? What is a Model Object?

Scheduling a variable change in one area of the model opens a gate in another place.

Variables hold the value of an entity’s name.

Many situations require a change-over or setup if the product changes. To track changes, the value of the past product must be stored in a variable and compared to the current product. If the product is different, then perform a setup.

Store the name in a variable and compare the current to the previous to see if it has changed.

An explanation of the previous example follows. Every entity entering this activity checks its current name (a_Name) against the value of the last name stored in a variable (v_PreviousName). If the name does not match, a setup time occurs, and the new name replaces the previous name in the variable. See the articles: What is an IF-Then statement? What is an Attribute? What is a Time statement?

Variables used in fields

Use variables in fields to modify information, such as times, or to check values to determine actions.

The condition is true if the “hour of day” is greater than 8:00 AM and less than 6:00 PM

 The largest variable values ProcessModel can use is: 2,147,483,647.

Display user-defined variables on the scoreboard or in a user-defined position during the simulation.